1. Field of the Invention
The present invention relates to a light deflector such as a rotating multiple-surface mirror or a hologram disk for use in various devices employing a laser beam such as a laser printer, a display, a flaw detector or a POS scanner.
2. Description of the Prior Art
Prior light deflectors such as rotating multiple-surface mirrors have been subjected to various problems that adversely affect optical characteristics of the deflectors. One of such difficulties is caused by jitter due to both a phase jitter resulting in cyclic rotational fluctuations of the motor which rotates the rotating miltiple-surface mirrors and a velocity instability resulting in time-dependent rotational fluctuations of the motor. The phase jitter is disadvantageous in that any line which would have to be drawn by the optical deflector perpendicularly to a main scanning direction or parallel to an auxiliary scanning direction tends to suffer from small vibrations. Any velocity instability, on the other hand, causes such a line to fluctuate in a greater cycle. In any case, these motor fluctuations impair the quality of an image printed or otherwise displayed.
It is known that, in general, as the speed of rotation of the rotating multiple-surface mirror or the motor is reduced, the fluctuations attributable to the phase jitter and the velocity instability are increased. Since the phase jitter and the velocity instability are correlated with each other, any reduction of the phase jitter can result in a reduction in fluctuations caused by the velocity instability.